I made an audio spectrum visualizer similar (After Effects) style like this one with multiple solid layers. But I have a problem: how to change the song in all layers at once? Every layer has different colours, glow and all other effects but the song is the same, so now if I want to change the song I have to go into every solid layer and change FX Audio Spectrum > Audio Layer > Song Name.
Using the Audio Spectrum plugin in After Effects, you can reference a layer (using the "Audio Layer" parameter) on your timeline as an audio source. To update all referenced audio sources in your project at once, you can precomp the audio track and use the new nested precomp as your audio source instead.
1) On your timeline, highlight your audio track. Hit CTRL + Shift + C (CMD + Shift + C on OSX) to Pre-compose the audio.
2) In the Pre-compose menu, name it "Audio Reference" or something similar, then select "Move all attributes into the new composition" and hit "OK"
3) This new composition will be added in your Project panel. Use this composition instead of your audio file when working in After Effects.
To update the audio file project-wide with a couple of clicks, just open the reference composition you created and swap out the audio file inside. This will change every instance of that composition in your project.
Hope this helps! Let me know if you need clarification.